The proposed training program is the centerpiece in efforts to provide postdoctoral training in laboratory genetics at Harvard Medical School. It has provided an opportunity to offer training to physicians and scientists in a wide variety of disciplines, enabling them to take advantage of the extraordinary rich environment offered at Harvard Medical School. It has also helped foster interactions between investigators, and provided a forum for increasing faculty contact with trainees in didactic sessions. The training units of the program include the HMS Department of Genetics, laboratories at Children's Hospital, Massachusetts General Hospital, Brigham and Women's Hospital, Dana Farber Cancer Institute, and Beth Israel Deaconess Medical Center. Although the focus of the training is on research the program is fully integrated with the Harvard Medical School Clinical Genetics Training Program. This program is accredited by the American Board of Medical Genetics in all areas of training (PhD Genetics, Cytogenetics, Biochemical Genetics, and Molecular Genetics) as well as by the American Council of Graduate Medical Education (MD Clinical Genetics). This provides an opportunity for trainees to become board eligible in a discipline of clinical genetics in addition to receive laboratory training. Fellowship training will be provided for two to three years. Support for ten postdoctoral trainees at level 4 or greater is requested.